CSS unit property optimization tips: em, rem, px and vw/vh

CSS unit attribute optimization tips: em, rem, px and vw/vh

Introduction:
In web design and development, CSS unit attributes play an important role Very important role. The correct selection and use of appropriate unit attributes can make the page display more beautiful and consistent on different devices and screen sizes. This article will introduce some commonly used CSS unit properties and provide specific code examples to help readers better master these optimization techniques.

em units:

em units are calculated relative to the font size of the parent element. For example, if the parent element's font size is set to 16px, then setting the font size of an element to 2em will result in its font size being 32px.

.parent {
  font-size: 16px;
}

.child {
  font-size: 2em;
}

rem units:

rem units are calculated relative to the font size of the root element. The root element is usually the element. The rem unit is simpler to calculate than the em unit. If the root element's font size is set to 16px, and an element's font size is 2rem, its font size will also be 32px.

html {
  font-size: 16px;
}

.child {
  font-size: 2rem;
}

px unit:

px unit is a fixed unit and is not affected by other elements. Set the font size of an element to 16px and its font size will always remain 16px.

.child {
  font-size: 16px;
}

vw/vh unit:

The vw unit is a percentage relative to the viewport width, 1vw is equal to 1% of the viewport width, and the vh unit is a percentage relative to the viewport height, 1vh is equal to 1% of the viewport height. These two units are very useful, especially in responsive designs.

.child {
  font-size: 5vw;
}

In the above code, if the viewport width is 1000px, the font size of this element will be 50px.

Conclusion:
When selecting and using CSS unit properties, you need to make choices based on different needs and scenarios. Em and rem units are for relative sizing settings, while px units are for fixed pixel sizes. vw/vh units work well with different screen sizes and viewport sizes.

Additional tips: This is just a simple example introduction. In actual use, it needs to be adjusted and optimized according to specific circumstances.

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